This invention relates to electrodeposition and coating systems for workpieces and more particularly to a unique and novel electrodeposition system utilizing a programmable hoist having an oscillating workpiece platform.
The present invention is best understood in the context of an electrodeposition or electropainting system wherein corrosive resistant coatings are applied to a workpiece such as a car body. It should be understood that the invention described below is not limited to car body applications and is applicable to any procedure for treating unfinished metal, especially where the geometry of the workpiece tends to entrap air and is not easily drained.
Prior to applying a finish coat of paint to a workpiece such as a car body, it has been necessary and desirable to apply corrosive resistant finishes to the workpiece under and over surfaces. One method of applying this finish is to use an electrodeposition or electropainting system. Prior electrodeposition or electropainting systems have utilized a series of extremely long and narrow immersion tanks with a monorail installed thereabove. Workpieces or car bodies are attached by carriers to the monorail and moved into and through the fluid within each immersion tank. A fluid, such as a pre-rinse, phosphating or electropainting solution is applied to the car body (workpiece) by virtue of the forward progression of the body within each tank. In addition to immersion tanks these systems may include a variety of spray booths for rinsing the body and heating or baking ovens for drying the finish. In such a system it has not been possible to apply a uniform protective coating to the various surfaces of the car body especially the car body undersurfaces where air is trapped. A further deficiency in these prior systems is that as the body is lifted from an immersion tank, a certain amount of fluid is retained in the cavities of the car body. As the car body is lifted from one tank and moved to another tank, this fluid is often carried into the adjacent tank contaminating the fluid therein or disturbing the process performed therein. Further these prior systems utilize large amounts of power since the bodies are wetted by virtue of their powered continuous motion through the various immersion tanks. In addition entrapped fluid may tend to cause the car body to float. Some additional considerations regarding these prior systems may be found in the document entitled "Recommended Design Considerations for the Use of PPG Electrodeposition Coatings" by PPG Industries, Inc., Springdale, Pa.
In contrast, the present invention comprises a system which minimizes drag-out of fluid, permits a uniform protective and sufficiently heavy coating of paint or material to be applied to the under and over surfaces of the workpiece. In addition, the system is flexible in design to accommodate a number of various physical arrangements. Accordingly, the present invention comprises:
A work processing system comprising: a plurality of work processing stations arranged in a predetermined sequence. These stations may include spray and immersion tanks, post rinse tanks, an electropainting tank and baking oven cells. The system further includes superstructure means suspended above the process stations, a programmable controller situated remote from the processing stations for generating command signals. A crane is suspended on and translatable relative to the superstructure and to the processing stations in response to the command signals. The system includes a work carrier unit carried by the crane and adapted to be suspended and supported by particular processing stations after insertion thereon. The crane further includes means for engaging and lifting and lowering the work carrier unit into and out of a respective one of the processing stations in response to control signals generated by the programmable controller. The work carrier unit comprises a work carrier member or platform adapted to support a workpiece and further includes means for rotating the work carrier member, platform, or workpiece about a predetermined axis thereof in response to command signals.
The system may further include sensors for monitoring the conditions within each processing station. The sensors transmit signals to the controller for storage and use by the controller.
Uniformity of paint application and reduced power requirements are achieved by the present invention by virtue of the fact that the workpiece can be lowered within an electropainting process station, tank, or cell and oscillated back and forth to remove entrapped air prior to applying power to the electrodes associated with the electropainting process station.